diff --git a/suite/common/src/nsSessionStore.js b/suite/common/src/nsSessionStore.js
index 15afa505a2..7447355dae 100644
--- a/suite/common/src/nsSessionStore.js
+++ b/suite/common/src/nsSessionStore.js
@@ -1462,25 +1462,60 @@ SessionStoreService.prototype = {
 
     let data = {};
     do {
+      let nId = node.id;
+      let hasDefaultValue = true;
+      let value;
+
       // Only generate a limited number of XPath expressions for perf reasons (cf. bug 477564)
-      if (!node.id && ++generatedCount > MAX_GENERATED_XPATHS)
+      if (!nId && generatedCount > MAX_GENERATED_XPATHS)
         continue;
 
-      let id = node.id ? "#" + node.id : XPathHelper.generate(node);
-      if (node instanceof Components.interfaces.nsIDOMHTMLInputElement) {
-        if (node.type != "file")
-          data[id] = node.type == "checkbox" || node.type == "radio" ? node.checked : node.value;
-        else
-          data[id] = { type: "file", fileList: node.mozGetFileNameArray() };
+      if (node instanceof Components.interfaces.nsIDOMHTMLInputElement ||
+          node instanceof Components.interfaces.nsIDOMHTMLTextAreaElement) {
+        switch (node.type) {
+          case "checkbox":
+          case "radio":
+            value = node.checked;
+            hasDefaultValue = value == node.defaultChecked;
+            break;
+          case "file":
+            value = { type: "file", fileList: node.mozGetFileNameArray() };
+            hasDefaultValue = !value.fileList.length;
+            break;
+          default: // text, textarea
+            value = node.value;
+            hasDefaultValue = value == node.defaultValue;
+            break;
+        }
+      }
+      else if (!node.multiple) {
+        // <select>s without the multiple attribute are hard to determine the
+        // default value, so assume we don't have the default.
+        hasDefaultValue = false;
+        value = node.selectedIndex;
       }
-      else if (node instanceof Components.interfaces.nsIDOMHTMLTextAreaElement)
-        data[id] = node.value;
-      else if (!node.multiple)
-        data[id] = node.selectedIndex;
       else {
-        let options = Array.map(node.options, function(aOpt, aIx) aOpt.selected ? aIx : -1);
-        data[id] = options.filter(function(aIx) aIx >= 0);
+        // <select>s with the multiple attribute are easier to determine the
+        // default value since each <option> has a defaultSelected
+        let options = Array.map(node.options, function(aOpt, aIx) {
+          let oSelected = aOpt.selected;
+          hasDefaultValue = hasDefaultValue && (oSelected == aOpt.defaultSelected);
+          return oSelected ? aIx : -1;
+        });
+        value = options.filter(function(aIx) aIx >= 0);
       }
+      // In order to reduce XPath generation (which is slow), we only save data
+      // for form fields that have been changed. (cf. bug 537289)
+      if (!hasDefaultValue) {
+        if (nId) {
+          data["#" + nId] = value;
+        }
+        else {
+          generatedCount++;
+          data[XPathHelper.generate(node)] = value;
+        }
+      }
+
     } while ((node = formNodes.iterateNext()));
 
     return data;
diff --git a/suite/common/tests/browser/browser_456342.js b/suite/common/tests/browser/browser_456342.js
index 1a492fb0fa..ea8c8ac264 100644
--- a/suite/common/tests/browser/browser_456342.js
+++ b/suite/common/tests/browser/browser_456342.js
@@ -50,34 +50,36 @@ function test() {
   
   let testURL = "chrome://mochikit/content/browser/" +
     "suite/common/tests/browser/browser_456342_sample.xhtml";
-  let tabbrowser = getBrowser();
-  let tab2 = tabbrowser.addTab("about:");
-  let tab = tabbrowser.addTab(testURL);
-  let browser = tab2.linkedBrowser;
-  browser.addEventListener("load", function(aEvent) {
+  let tab = getBrowser().addTab(testURL);
+  tab.linkedBrowser.addEventListener("load", function(aEvent) {
     this.removeEventListener("load", arguments.callee, true);
-    browser.addEventListener("pageshow", function(aEvent) {
-      browser.removeEventListener("pageshow", arguments.callee, true);
-      let undoItems = JSON.parse(ss.getClosedTabData(window));
-      let savedFormData = undoItems[0].state.entries[0].formdata;
-      
-      let countGood = 0, countBad = 0;
-      for each (let value in savedFormData) {
-        if (value == "save me")
-          countGood++;
-        else
-          countBad++;
-      }
-      
-      is(countGood, 4, "Saved text for non-standard input fields");
-      is(countBad,  0, "Didn't save text for ignored field types");
-      
-      // clean up
-      if (gPrefService.prefHasUserValue("browser.sessionstore.privacy_level"))
-        gPrefService.clearUserPref("browser.sessionstore.privacy_level");
-      tabbrowser.removeTab(tab2);
-      finish();
-    }, true);
-    tabbrowser.removeTab(tab);
+
+    let expectedValue = "try to save me";
+    // Since bug 537289 we only save non-default values, so we need to set each
+    // form field's value after load.
+    let formEls = aEvent.originalTarget.forms[0].elements;
+    for (let i = 0; i < formEls.length; i++)
+      formEls[i].value = expectedValue;
+
+    getBrowser().removeTab(tab);
+    
+    let undoItems = JSON.parse(ss.getClosedTabData(window));
+    let savedFormData = undoItems[0].state.entries[0].formdata;
+    
+    let countGood = 0, countBad = 0;
+    for each (let value in savedFormData) {
+      if (value == expectedValue)
+        countGood++;
+      else
+        countBad++;
+    }
+    
+    is(countGood, 4, "Saved text for non-standard input fields");
+    is(countBad,  0, "Didn't save text for ignored field types");
+    
+    // clean up
+    if (gPrefService.prefHasUserValue("browser.sessionstore.privacy_level"))
+      gPrefService.clearUserPref("browser.sessionstore.privacy_level");
+    finish();
   }, true);
 }
diff --git a/suite/common/tests/browser/browser_456342_sample.xhtml b/suite/common/tests/browser/browser_456342_sample.xhtml
index 183f805820..f0b0005b77 100644
--- a/suite/common/tests/browser/browser_456342_sample.xhtml
+++ b/suite/common/tests/browser/browser_456342_sample.xhtml
@@ -5,22 +5,24 @@
 <head><title>Test for bug 456342</title></head>
 
 <body>
+<form>
 <h3>Non-standard &lt;input&gt;s</h3>
-<p>Search        <input type="search"       value="save me" id="searchTerm"/></p>
-<p>Image Search: <input type="image search" value="save me" /></p>
-<p>Autocomplete: <input type="autocomplete" value="save me" name="fill-in"/></p>
-<p>Mistyped:     <input type="txet"         value="save me" name="mistyped"/></p>
+<p>Search        <input type="search"       id="searchTerm"/></p>
+<p>Image Search: <input type="image search" /></p>
+<p>Autocomplete: <input type="autocomplete" name="fill-in"/></p>
+<p>Mistyped:     <input type="txet"         name="mistyped"/></p>
 
 <h3>Ignored types</h3>
-<input type="hidden" value="don't save" name="hideme"/>
-<input type="HIDDEN" value="don't save" name="hideme2"/>
-<input type="submit" value="don't save" name="submit"/>
-<input type="reset"  value="don't save" name="reset"/>
-<input type="image"  value="don't save" name="image"/>
-<input type="button" value="don't save" name="button"/>
-<input type="password" value="don't save" name="password"/>
-<input type="PassWord" value="don't save" name="password2"/>
-<input type="PASSWORD" value="don't save" name="password3"/>
+<input type="hidden" name="hideme"/>
+<input type="HIDDEN" name="hideme2"/>
+<input type="submit" name="submit"/>
+<input type="reset"  name="reset"/>
+<input type="image"  name="image"/>
+<input type="button" name="button"/>
+<input type="password" name="password"/>
+<input type="PassWord" name="password2"/>
+<input type="PASSWORD" name="password3"/>
+</form>
 
 </body>
 </html>